1. Field of the Invention
The present invention relates generally to improved methods for indirect bonding of orthodontic appliances, such as brackets, to the tooth surfaces of dental patients. The methods use a transfer tray to accurately position the brackets on the tooth surfaces. Dental materials are used to bond the brackets to the teeth. The tray is then removed from the mouth, while the appliances remain firmly bonded to the tooth surfaces. One advantage of the tray system is the tray material securely holds the brackets and blocks out all bracket undercuts.
2. Brief Description of the Related Art
Orthodontic treatment is performed to move poorly positioned teeth to new locations, which leads to improved occlusion of opposing teeth in the oral cavity. The motivation for orthodontic treatment can be improved appearance, correction of congenital defects, reduction of temporal-mandibular joint pain, enhanced masticatory function, alleviation of trauma-induced mal-positioning of teeth, correction of age-related tooth movement due to loss of other teeth or the eruption of third molars, or reduction of periodontal trauma caused by malocclusion.
Orthodontic appliances (bands, brackets, anchorage devices, and occlusal separators) are commonly bonded to each tooth individually, and a wire in the lower and upper dental arch connects the appliances. The placement of these appliances on each tooth is of the utmost important to the treatment for each tooth's position with regard to moving the teeth to the desired orthodontic position. If the appliance is applied too closely or too distantly from the gingival tissue, the tooth may move to a position that is unduly intruded or extruded. Similarly, if improperly placed, the desired rotation or torque may not be applied to the tooth to ensure its correct alignment in the dental arch.
In general, there are two techniques for bonding the orthodontic appliances to the tooth surfaces of the patient: i) direct bonding and ii) indirect bonding. In a direct bonding method, the appliance is placed directly on the tooth surface. The base of the appliance and/or tooth surface must be coated with adhesive. Once the appliance is properly positioned, the adhesive is cured to bond the appliance in place. Light-curing, and chemical (self)-curing, and dual-curing adhesives may be employed. While the direct bonding technique is commonly used, it can have some disadvantages. For instance, it can be difficult for the practitioner to accurately place the appliance in its intended location. The appliance may shift slightly as it is being bonded on the tooth surface. The process can be time-consuming as each appliance must be precisely positioned and then bonded in place with limited time and limited vision into the oral cavity.
In an indirect bonding method, a dental laboratory or clinician makes a transfer tray having the shape of a patient's dental anatomy. A set of appliances is releasably attached to the transfer tray. When the patient is ready, the base of the appliance and/or tooth surfaces must be coated with adhesive. The transfer tray is then placed in the patient's mouth and pressed over the patient's teeth until the adhesive cures. The tray is then removed from the mouth, while the appliances remain firmly bonded to the tooth surfaces. Thus, the appliances are transferred from the tray and become bonded to the tooth surfaces at their desired locations. Some indirect bonding techniques are generally described in the literature. Early techniques as described in Cohen and Silverman, U.S. Pat. No. 3,738,005, required engagement of the tray into the hooks and undercuts of the brackets for transfer.
Recent methods, as described in Cleary et al., U.S. Pat. Nos. 7,020,963, 7,404,714, 7,410,357, and 7,188,421 use an indirect bonding tray that is made by initially placing spacer material, such as silicone, over a replica of the patient's tooth structure. A tray is then formed over the spacer material and hardened. Once the tray has hardened, the tray is detached from the spacer material. Next, the spacer material is removed from the tooth replica and set aside. The orthodontic appliances are placed on the replica at the desired locations. A silicone matrix or dental impression material is placed between the tray and replica and allowed to harden. Then, the tray assembly can be removed from the replica for insertion in the patient's mouth and the brackets can be transferred and bonded to the patient's teeth.
Although some indirect bonding techniques are generally effective for bonding orthodontic appliances, there is a need for improved methods. The present invention provides such improved methods.